Multi-tier write allocation

ABSTRACT

Techniques are provided for multi-tier write allocation. A storage system may store data within a multi-tier storage environment comprising a first storage tier (e.g., storage devices maintained by the storage system), a second storage tier (e.g., a remote object store provided by a third party storage provider), and/or other storage tiers. A determination is made that data (e.g., data of a write request received by the storage system) is to be stored within the second storage tier. The data is stored into a staging area of the first storage tier. A second storage tier location identifier, for referencing the data according to a format utilized by the second storage tier, is assigned to the data and provided to a file system hosting the data. The data is then destaged from the staging area into the second storage tier, such as within an object stored within the remote object store.

RELATED APPLICATIONS

This application claims priority to and is a continuation of U.S.application Ser. No. 17/833,046, filed on Jun. 6, 2022, titled“MULTI-TIER DESTAGING WRITE ALLOCATION,” which claims priority to and isa continuation of U.S. Pat. No. 11,350,049, filed on Nov. 11, 2019,titled “MULTI-TIER DESTAGING WRITE ALLOCATION,” which claims priority toand is a continuation of U.S. Pat. No. 10,489,073, filed on Apr. 28,2017, titled “MULTI-TIER WRITE ALLOCATION”, which are incorporatedherein

BACKGROUND

Many storage systems may provide clients with access to data storedwithin a plurality of storage devices. For example, a storage controllermay store client data within a set of storage devices that are locallyaccessible (e.g., locally attached to the storage controller) orremotely accessible (e.g., accessible over a network). A storageaggregate of storage (e.g., a composite aggregate comprising a set ofvolumes) may be generated from the set of storage devices (e.g., thestorage aggregate may be stored across one or more storage devices). Thestorage aggregate may be exported from a storage file system to aclient. The storage aggregate may appear as one or more storagecontainers to the client, such as a volume or logical unit number (lun).In this way, the storage aggregate abstracts away the details, from theclient, of how the storage aggregate is physically stored amongst theset of storage devices.

Some storage systems may store data within a multi-tiered storageenvironment. For example, the storage controller may store data within ahard disk drive tier and a solid state storage tier. The hard disk drivetier may be used as a capacity tier to store client data and forprocessing input/output operations. The solid state storage tier may beused as a cache for accelerating the processing of storage operations.Different storage tiers have different characteristics and behaviors,which can affect performance and guarantees provided to clients by astorage system.

In an example, a storage system may utilize a storage tier (e.g., alocal storage tier hosted, owned, and/or managed by one or more nodes ofa storage environment associated with the storage system) and a remoteobject store as two of the storage tiers within which the storage systemstores data. The storage system may be able to provide highavailability, security, data consistency, data protection, and/or otherguarantees using the storage tier because the storage system may manageand control the storage tier. However, the storage system may be unableto provide similar guarantees, such as that data is properly stored,managed, is consistent, and is accurate, to clients for the remoteobject store because the storage system does not manage and control theremote object store (e.g., a third party provider may host and managethe remote object store). For example, new data could be written to aremote third party object store. When reading the new data, old data orno data could be returned by the remote third party object store due todelay. Thus, the storage system may be unable to provide the same levelof enterprise guarantees and efficiencies when working with the remotethird party object store as backend storage.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a component block diagram illustrating an example clusterednetwork in accordance with one or more of the provisions set forthherein.

FIG. 2 is a component block diagram illustrating an example data storagesystem in accordance with one or more of the provisions set forthherein.

FIG. 3 is a flow chart illustrating an exemplary method of multi-tierwrite allocation.

FIG. 4A is a component block diagram illustrating an exemplary computingdevice for multi-tier write allocation, where data is identified forstorage within a multi-tier storage environment.

FIG. 4B is a component block diagram illustrating an exemplary computingdevice for multi-tier write allocation, where data is staged within afirst storage tier.

FIG. 4C is a component block diagram illustrating an exemplary computingdevice for multi-tier write allocation, where data is destaged to asecond storage tier.

FIG. 5 is an example of a computer readable medium in accordance withone or more of the provisions set forth herein.

DETAILED DESCRIPTION

Some examples of the claimed subject matter are now described withreference to the drawings, where like reference numerals are generallyused to refer to like elements throughout. In the following description,for purposes of explanation, numerous specific details are set forth inorder to provide an understanding of the claimed subject matter. It maybe evident, however, that the claimed subject matter may be practicedwithout these specific details. Nothing in this detailed description isadmitted as prior art.

One or more techniques and/or computing devices for multi-tier writeallocation are provided herein. A storage system may utilize multipletiers of storage to store client data. For example, the storage systemmay utilize a first storage tier (e.g., a performance storage tier, suchas a solid state storage tier or a hard disk drive storage tier, locallyhosted and/or maintained by nodes of a storage environment associatedwith the storage system), a second storage tier such as a remote objectstore (e.g., a distributed network of storage provided by a third partyprovider, cloud storage, etc.), and/or other tiers of storage.

Because the first storage tier may provide lower latency than the remoteobject store, more frequently accessed or more recently accessed data(e.g., hot data) may be stored within the first storage tier. Lessfrequently accessed or less recently accessed data (e.g., cold data) maybe migrated from the first storage tier to the second storage tier.Unfortunately, a substantial amount of resources, time, and delay may beintroduced when data is stored within the first storage tier for accessby a file system using a storage format of the first storage tier (e.g.,an addressing or naming scheme), temperatures are tracked for datablocks, and cold data blocks are moved from the first storage tier tothe second storage tier for access by the file system using a storageformat of the second storage tier. The file system must be updated toutilize the storage format of the second storage tier for each of thecold data blocks now stored within the second storage tier.

Accordingly, as provided herein, data may be identified for storagewithin the second storage tier based upon an application specifyingsuch, the data being associated with a policy (e.g., a mirroring policy,a snapshot policy, etc.), the data being stored within a particular typeof volume such as a backup volume, and/or other indicators (e.g.,indicators of data known or expected to be cold). Instead of firststoring the data within the first storage tier for access by the filesystem using the storage format of the first storage tier, the data isstored within a staging area of the first storage tier. A second storagetier location identifier, corresponding to the storage format of thesecond storage tier, is assigned to the data (e.g., a physical volumeblock number (pvbn) used by the second storage tier such as a remoteobject store hosted by a third party storage provider such as a cloudstorage provider). The second storage tier location identifier may beprovided to the file system. In this way, the data can be destaged tothe second storage tier (e.g., stored as an object within the remoteobject store) in a consistent manner without the need to change how thefile system references the data because the file system was alreadyconfigured to utilize the second storage tier location identifier.

To provide for multi-tier write allocation, FIG. 1 illustrates anembodiment of a clustered network environment 100 or a network storageenvironment. It may be appreciated, however, that the techniques, etc.described herein may be implemented within the clustered networkenvironment 100, a non-cluster network environment, and/or a variety ofother computing environments, such as a desktop computing environment.That is, the instant disclosure, including the scope of the appendedclaims, is not meant to be limited to the examples provided herein. Itwill be appreciated that where the same or similar components, elements,features, items, modules, etc. are illustrated in later figures but werepreviously discussed with regard to prior figures, that a similar (e.g.,redundant) discussion of the same may be omitted when describing thesubsequent figures (e.g., for purposes of simplicity and ease ofunderstanding).

FIG. 1 is a block diagram illustrating the clustered network environment100 that may implement at least some embodiments of the techniquesand/or systems described herein. The clustered network environment 100comprises data storage systems 102 and 104 that are coupled over acluster fabric 106, such as a computing network embodied as a privateInfiniband, Fibre Channel (FC), or Ethernet network facilitatingcommunication between the data storage systems 102 and 104 (and one ormore modules, component, etc. therein, such as, nodes 116 and 118, forexample). It will be appreciated that while two data storage systems 102and 104 and two nodes 116 and 118 are illustrated in FIG. 1 , that anysuitable number of such components is contemplated. In an example, nodes116, 118 comprise storage controllers (e.g., node 116 may comprise aprimary or local storage controller and node 118 may comprise asecondary or remote storage controller) that provide client devices,such as host devices 108, 110, with access to data stored within datastorage devices 128, 130. Similarly, unless specifically providedotherwise herein, the same is true for other modules, elements,features, items, etc. referenced herein and/or illustrated in theaccompanying drawings. That is, a particular number of components,modules, elements, features, items, etc. disclosed herein is not meantto be interpreted in a limiting manner.

It will be further appreciated that clustered networks are not limitedto any particular geographic areas and can be clustered locally and/orremotely. Thus, in one embodiment a clustered network can be distributedover a plurality of storage systems and/or nodes located in a pluralityof geographic locations; while in another embodiment a clustered networkcan include data storage systems (e.g., 102, 104) residing in a samegeographic location (e.g., in a single onsite rack of data storagedevices).

In the illustrated example, one or more host devices 108, 110 which maycomprise, for example, client devices, personal computers (PCs),computing devices used for storage (e.g., storage servers), and othercomputers or peripheral devices (e.g., printers), are coupled to therespective data storage systems 102, 104 by storage network connections112, 114. Network connection may comprise a local area network (LAN) orwide area network (WAN), for example, that utilizes Network AttachedStorage (NAS) protocols, such as a Common Internet File System (CIFS)protocol or a Network File System (NFS) protocol to exchange datapackets, a Storage Area Network (SAN) protocol, such as Small ComputerSystem Interface (SCSI) or Fiber Channel Protocol (FCP), an objectprotocol, such as S3, etc. Illustratively, the host devices 108, 110 maybe general-purpose computers running applications, and may interact withthe data storage systems 102, 104 using a client/server model forexchange of information. That is, the host device may request data fromthe data storage system (e.g., data on a storage device managed by anetwork storage control configured to process I/O commands issued by thehost device for the storage device), and the data storage system mayreturn results of the request to the host device via one or more storagenetwork connections 112, 114.

The nodes 116, 118 on clustered data storage systems 102, 104 cancomprise network or host nodes that are interconnected as a cluster toprovide data storage and management services, such as to an enterprisehaving remote locations, cloud storage (e.g., a storage endpoint may bestored within a data cloud), etc., for example. Such a node in theclustered network environment 100 can be a device attached to thenetwork as a connection point, redistribution point or communicationendpoint, for example. A node may be capable of sending, receiving,and/or forwarding information over a network communications channel, andcould comprise any device that meets any or all of these criteria. Oneexample of a node may be a data storage and management server attachedto a network, where the server can comprise a general purpose computeror a computing device particularly configured to operate as a server ina data storage and management system.

In an example, a first cluster of nodes such as the nodes 116, 118(e.g., a first set of storage controllers configured to provide accessto a first storage aggregate comprising a first logical grouping of oneor more storage devices) may be located on a first storage site. Asecond cluster of nodes, not illustrated, may be located at a secondstorage site (e.g., a second set of storage controllers configured toprovide access to a second storage aggregate comprising a second logicalgrouping of one or more storage devices). The first cluster of nodes andthe second cluster of nodes may be configured according to a disasterrecovery configuration where a surviving cluster of nodes providesswitchover access to storage devices of a disaster cluster of nodes inthe event a disaster occurs at a disaster storage site comprising thedisaster cluster of nodes (e.g., the first cluster of nodes providesclient devices with switchover data access to storage devices of thesecond storage aggregate in the event a disaster occurs at the secondstorage site).

As illustrated in the clustered network environment 100, nodes 116, 118can comprise various functional components that coordinate to providedistributed storage architecture for the cluster. For example, the nodescan comprise network modules 120, 122 and disk modules 124, 126. Networkmodules 120, 122 can be configured to allow the nodes 116, 118 (e.g.,network storage controllers) to connect with host devices 108, 110 overthe storage network connections 112, 114, for example, allowing the hostdevices 108, 110 to access data stored in the distributed storagesystem. Further, the network modules 120, 122 can provide connectionswith one or more other components through the cluster fabric 106. Forexample, in FIG. 1 , the network module 120 of node 116 can access asecond data storage device by sending a request through the disk module126 of node 118.

Disk modules 124, 126 can be configured to connect one or more datastorage devices 128, 130, such as disks or arrays of disks, flashmemory, or some other form of data storage, to the nodes 116, 118. Thenodes 116, 118 can be interconnected by the cluster fabric 106, forexample, allowing respective nodes in the cluster to access data on datastorage devices 128, 130 connected to different nodes in the cluster.Often, disk modules 124, 126 communicate with the data storage devices128, 130 according to the SAN protocol, such as SCSI or FCP, forexample. Thus, as seen from an operating system on nodes 116, 118, thedata storage devices 128, 130 can appear as locally attached to theoperating system. In this manner, different nodes 116, 118, etc. mayaccess data blocks through the operating system, rather than expresslyrequesting abstract files.

It should be appreciated that, while the clustered network environment100 illustrates an equal number of network and disk modules, otherembodiments may comprise a differing number of these modules. Forexample, there may be a plurality of network and disk modulesinterconnected in a cluster that does not have a one-to-onecorrespondence between the network and disk modules. That is, differentnodes can have a different number of network and disk modules, and thesame node can have a different number of network modules than diskmodules.

Further, a host device 108, 110 can be networked with the nodes 116, 118in the cluster, over the storage networking connections 112, 114. As anexample, respective host devices 108, 110 that are networked to acluster may request services (e.g., exchanging of information in theform of data packets) of nodes 116, 118 in the cluster, and the nodes116, 118 can return results of the requested services to the hostdevices 108, 110. In one embodiment, the host devices 108, 110 canexchange information with the network modules 120, 122 residing in thenodes 116, 118 (e.g., network hosts) in the data storage systems 102,104.

In one embodiment, the data storage devices 128, 130 comprise volumes132, which is an implementation of storage of information onto diskdrives or disk arrays or other storage (e.g., flash) as a file-systemfor data, for example. In an example, a disk array can include alltraditional hard drives, all flash drives, or a combination oftraditional hard drives and flash drives. Volumes can span a portion ofa disk, a collection of disks, or portions of disks, for example, andtypically define an overall logical arrangement of file storage on diskspace in the storage system. In one embodiment a volume can comprisestored data as one or more files that reside in a hierarchical directorystructure within the volume.

Volumes are typically configured in formats that may be associated withparticular storage systems, and respective volume formats typicallycomprise features that provide functionality to the volumes, such asproviding an ability for volumes to form clusters. For example, where afirst storage system may utilize a first format for their volumes, asecond storage system may utilize a second format for their volumes.

In the clustered network environment 100, the host devices 108, 110 canutilize the data storage systems 102, 104 to store and retrieve datafrom the volumes 132. In this embodiment, for example, the host device108 can send data packets to the network module 120 in the node 116within data storage system 102. The node 116 can forward the data to thedata storage device 128 using the disk module 124, where the datastorage device 128 comprises volume 132A. In this way, in this example,the host device can access the volume 132A, to store and/or retrievedata, using the data storage system 102 connected by the storage networkconnection 112. Further, in this embodiment, the host device 110 canexchange data with the network module 122 in the node 118 within thedata storage system 104 (e.g., which may be remote from the data storagesystem 102). The node 118 can forward the data to the data storagedevice 130 using the disk module 126, thereby accessing volume 132Bassociated with the data storage device 130.

It may be appreciated that multi-tier write allocation may beimplemented within the clustered network environment 100. In an example,the node 116 and/or the node 118 may utilize a multi-tier storageenvironment such as a remote object store and/or the data storagedevices 128, 130 for serving client requests. It may be appreciated thatmulti-tier write allocation may be implemented for and/or between anytype of computing environment, and may be transferrable between physicaldevices (e.g., node 116, node 118, a desktop computer, a tablet, alaptop, a wearable device, a mobile device, a storage device, a server,etc.) and/or a cloud computing environment (e.g., remote to theclustered network environment 100).

FIG. 2 is an illustrative example of a data storage system 200 (e.g.,102, 104 in FIG. 1 ), providing further detail of an embodiment ofcomponents that may implement one or more of the techniques and/orsystems described herein. The data storage system 200 comprises a node202 (e.g., nodes 116, 118 in FIG. 1 ), and a data storage device 234(e.g., data storage devices 128, 130 in FIG. 1 ). The node 202 may be ageneral purpose computer, for example, or some other computing deviceparticularly configured to operate as a storage server. A host device205 (e.g., 108, 110 in FIG. 1 ) can be connected to the node 202 over anetwork 216, for example, to provide access to files and/or other datastored on the data storage device 234. In an example, the node 202comprises a storage controller that provides client devices, such as thehost device 205, with access to data stored within data storage device234.

The data storage device 234 can comprise mass storage devices, such asdisks 224, 226, 228 of a disk array 218, 220, 222. It will beappreciated that the techniques and systems, described herein, are notlimited by the example embodiment. For example, disks 224, 226, 228 maycomprise any type of mass storage devices, including but not limited tomagnetic disk drives, flash memory, and any other similar media adaptedto store information, including, for example, data (D) and/or parity (P)information.

The node 202 comprises one or more processors 204, a memory 206, anetwork adapter 210, a cluster access adapter 212, and a storage adapter214 interconnected by a system bus 242. The data storage system 200 alsoincludes an operating system 208 installed in the memory 206 of the node202 that can, for example, implement a Redundant Array of Independent(or Inexpensive) Disks (RAID) optimization technique to optimize areconstruction process of data of a failed disk in an array.

The operating system 208 can also manage communications for the datastorage system, and communications between other data storage systemsthat may be in a clustered network, such as attached to a cluster fabric215 (e.g., 106 in FIG. 1 ). Thus, the node 202, such as a networkstorage controller, can respond to host device requests to manage dataon the data storage device 234 (e.g., or additional clustered devices)in accordance with these host device requests. The operating system 208can often establish one or more file systems on the data storage system200, where a file system can include software code and data structuresthat implement a persistent hierarchical namespace of files anddirectories, for example. As an example, when a new data storage device(not shown) is added to a clustered network system, the operating system208 is informed where, in an existing directory tree, new filesassociated with the new data storage device are to be stored. This isoften referred to as “mounting” a file system.

In the example data storage system 200, memory 206 can include storagelocations that are addressable by the processors 204 and adapters 210,212, 214 for storing related software application code and datastructures. The processors 204 and adapters 210, 212, 214 may, forexample, include processing elements and/or logic circuitry configuredto execute the software code and manipulate the data structures. Theoperating system 208, portions of which are typically resident in thememory 206 and executed by the processing elements, functionallyorganizes the storage system by, among other things, invoking storageoperations in support of a file service implemented by the storagesystem. It will be apparent to those skilled in the art that otherprocessing and memory mechanisms, including various computer readablemedia, may be used for storing and/or executing application instructionspertaining to the techniques described herein. For example, theoperating system can also utilize one or more control files (not shown)to aid in the provisioning of virtual machines.

The network adapter 210 includes the mechanical, electrical andsignaling circuitry needed to connect the data storage system 200 to ahost device 205 over a network 216, which may comprise, among otherthings, a point-to-point connection or a shared medium, such as a localarea network. The host device 205 (e.g., 108, 110 of FIG. 1 ) may be ageneral-purpose computer configured to execute applications. Asdescribed above, the host device 205 may interact with the data storagesystem 200 in accordance with a client/host model of informationdelivery.

The storage adapter 214 cooperates with the operating system 208executing on the node 202 to access information requested by the hostdevice 205 (e.g., access data on a storage device managed by a networkstorage controller). The information may be stored on any type ofattached array of writeable media such as magnetic disk drives, flashmemory, and/or any other similar media adapted to store information. Inthe example data storage system 200, the information can be stored indata blocks on the disks 224, 226, 228. The storage adapter 214 caninclude input/output (I/O) interface circuitry that couples to the disksover an I/O interconnect arrangement, such as a storage area network(SAN) protocol (e.g., Small Computer System Interface (SCSI), iSCSI,hyperSCSI, Fiber Channel Protocol (FCP)). The information is retrievedby the storage adapter 214 and, if necessary, processed by the one ormore processors 204 (or the storage adapter 214 itself) prior to beingforwarded over the system bus 242 to the network adapter 210 (and/or thecluster access adapter 212 if sending to another node in the cluster)where the information is formatted into a data packet and returned tothe host device 205 over the network 216 (and/or returned to anothernode attached to the cluster over the cluster fabric 215).

In one embodiment, storage of information on disk arrays 218, 220, 222can be implemented as one or more storage volumes 230, 232 that arecomprised of a cluster of disks 224, 226, 228 defining an overalllogical arrangement of disk space. The disks 224, 226, 228 that compriseone or more volumes are typically organized as one or more groups ofRAIDs. As an example, volume 230 comprises an aggregate of disk arrays218 and 220, which comprise the cluster of disks 224 and 226.

In one embodiment, to facilitate access to disks 224, 226, 228, theoperating system 208 may implement a file system (e.g., write anywherefile system) that logically organizes the information as a hierarchicalstructure of directories and files on the disks. In this embodiment,respective files may be implemented as a set of disk blocks configuredto store information, whereas directories may be implemented asspecially formatted files in which information about other files anddirectories are stored.

Whatever the underlying physical configuration within this data storagesystem 200, data can be stored as files within physical and/or virtualvolumes, which can be associated with respective volume identifiers,such as file system identifiers (FSIDs), which can be 32-bits in lengthin one example.

A physical volume corresponds to at least a portion of physical storagedevices whose address, addressable space, location, etc. doesn't change,such as at least some of one or more data storage devices 234 (e.g., aRedundant Array of Independent (or Inexpensive) Disks (RAID system)).Typically the location of the physical volume doesn't change in that the(range of) address(es) used to access it generally remains constant.

A virtual volume, in contrast, is stored over an aggregate of disparateportions of different physical storage devices. The virtual volume maybe a collection of different available portions of different physicalstorage device locations, such as some available space from each of thedisks 224, 226, and/or 228. It will be appreciated that since a virtualvolume is not “tied” to any one particular storage device, a virtualvolume can be said to include a layer of abstraction or virtualization,which allows it to be resized and/or flexible in some regards.

Further, a virtual volume can include one or more logical unit numbers(LUNs) 238, directories 236, Qtrees 235, and files 240. Among otherthings, these features, but more particularly LUNS, allow the disparatememory locations within which data is stored to be identified, forexample, and grouped as data storage unit. As such, the LUNs 238 may becharacterized as constituting a virtual disk or drive upon which datawithin the virtual volume is stored within the aggregate. For example,LUNs are often referred to as virtual drives, such that they emulate ahard drive from a general purpose computer, while they actually comprisedata blocks stored in various parts of a volume.

In one embodiment, one or more data storage devices 234 can have one ormore physical ports, wherein each physical port can be assigned a targetaddress (e.g., SCSI target address). To represent respective volumesstored on a data storage device, a target address on the data storagedevice can be used to identify one or more LUNs 238. Thus, for example,when the node 202 connects to a volume 230, 232 through the storageadapter 214, a connection between the node 202 and the one or more LUNs238 underlying the volume is created.

In one embodiment, respective target addresses can identify multipleLUNs, such that a target address can represent multiple volumes. The I/Ointerface, which can be implemented as circuitry and/or software in thestorage adapter 214 or as executable code residing in memory 206 andexecuted by the processors 204, for example, can connect to volume 230by using one or more addresses that identify the one or more LUNs 238.

It may be appreciated that multi-tier write allocation may beimplemented for the data storage system 200. In an example, the node 202may utilize a multi-tier storage environment such as a remote objectstore and/or other storage tiers for serving client requests. It may beappreciated that multi-tier write allocation may be implemented forand/or between any type of computing environment, and may betransferrable between physical devices (e.g., node 202, host device 205,a desktop computer, a tablet, a laptop, a wearable device, a mobiledevice, a storage device, a server, etc.) and/or a cloud computingenvironment (e.g., remote to the node 202 and/or the host device 205).

One embodiment of multi-tier write allocation is illustrated by anexemplary method 300 of FIG. 3 . A storage system may provide clientswith access to client data stored within a backend such as a multi-tierstorage environment. The backend may be configured with one or moretiers of storage. For example, the backend may be configured with afirst storage tier (e.g., solid state drives, hard disk drives, etc.), asecond storage tier such as a remote object store (e.g., a third partystorage provider, cloud storage, etc.), etc.

The storage system may store data within the first storage tier as aperformance tier for frequently or recently accessed data because thefirst storage tier may have lower latency and more guarantees than thesecond storage tier such as the remote object store. The storage systemmay migrate data from the first storage tier to the second storage tier(e.g., less frequently or less recently accessed data) or may store newdata to the remote object store. In an example, the first storage tiercomprises storage devices hosted by a storage environment of the storagesystem (e.g., clusters of nodes may store data with storage devicesowned and managed by such nodes) that manages client access to volumeswhose data is stored across the multi-tier storage environment. Thesecond storage tier comprises a remote object store hosted by a thirdparty storage provider and not the storage environment. The firststorage tier may have lower latency and improved consistency guaranteesthan the second storage tier because the storage environment hosts andmanages the first storage tier.

The storage system may create a composite aggregate composed of a set ofvolumes that are exposed to clients. Data of the set of volumes may bestored within the multi-tier storage environment such as within thefirst storage tier and as objects within the remote object store of thesecond storage tier. An object may be assigned a name based upon avolume identifier of a volume (e.g., a buftree UUID uniquely identifyingthe volume), of the composite aggregate, to which the object belongs.For example, a prefix of the name may be derived from the volumeidentifier. The name may also be derived from a sequence number uniquelyassigned to the object. For example, the prefix of the name may bederived from the sequence number. Monotonically increasing sequencenumbers may be assigned to objects that are created within the remoteobject store for a volume (e.g., sequence numbers may be unique for aparticular buftree UUID, but not across buftree UUIDs of other volumes).In an example, the name of the object may be derived from a hash for thevolume identifier and/or the sequence number.

The storage system may store objects within the remote object store. Anobject may comprise a header. The header may comprise a version of theobject, an indicator as to whether the object is encrypted, a creationtimestamp for the object, a volume identifier (e.g., a buff treeuniversal identifier such as a buftree UUID), an identifier of a name ofthe object (e.g., a hash of the name and the buftree UUID, which can beread back after a put operation of the object into the remote objectstore to verify the hash), and/or other information. In one example, theheader is 32 bytes or any other size of information.

The object may comprise one or more object pages corresponding to datachunks, such as data chunks derived from data moved from the firststorage tier (e.g., a performance storage tier, such as a solid statestorage tier or a disk storage tier) of the storage system to the remoteobject store. In one example, the object may comprise space for 1024object pages, such as a first object page, a second object page, and/orother object pages. The first object page may comprise a first datachunk (e.g., 4 kilobytes of data or any other size of data) and a firstcontext associated with the first object page.

The first context may comprise an indicator as to whether the object isencrypted. The first context may comprise an encryption key index usedto identify an encryption key. The first context may comprise apseudobad indicator to indicate whether data read from the local storagetier had an error such as a disk error and the data content in theobject is inconsistent. The first context may comprise an indicator asto whether a RAID or storage OS marked the pseudobad error. The firstcontext may comprise an unverified error indicator to indicate that whendata read from the local storage tier resulted in an unverified RAIDerror. The first context may comprise a wrecked indicator that is setwhen data is forcefully corrupted. The first context may comprise a fileblock number (e.g., a location of the file block number for the firstdata chunk within the first volume). The first context may comprise achecksum for the first data chunk and the first context. In an example,the first context may comprise 16 bytes of information or any other sizeof information.

At 302, data that is to be stored within the multi-tiered storageenvironment, comprising the first storage tier (e.g., storage deviceshosted, owned, and/or managed by nodes and/or clusters of a storageenvironment that stores client data within the multi-tiered storageenvironment), the second storage tier (e.g., the remote object storemaintained by a third party provider), and/or other storage tiers, maybe identified. In one embodiment, the data may be received from anapplication (e.g., a snapshot creation application, a backupapplication, etc.) that specifies a property of the data and/or providesan indication into which type of storage tier the data should be stored.For example, the application may specify that the data is cold data(e.g., accessed below a frequency metric), and thus should be stored inthe remote object store configured to store cold data.

At 304, a determination is made that the data is to be stored within thesecond storage tier and not the first storage tier of the multi-tieredstorage environment. In one example, the determination is made basedupon the application providing an indication that the data is to bestored within the second storage tier, such as an indication that thedata is cold (e.g., backup data, infrequently accessed data, data notrecently accessed, etc.) and that the second storage tier is to storecold data whereas the first storage tier is to store hot data (e.g.,frequently or recently accessed data) because the first storage tier mayhave less latency than the second storage tier. In an example, theindication may specify that the data is accessed below a frequencymetric (cold data).

In another example, the determination is made based upon a property of avolume to which the data belongs. For example, the data may comprisebackup data that is being backed up from a source volume to adestination backup volume. The destination backup volume may comprise abackup property specifying that the destination backup volume is beingused for backing up data. The second storage tier may be designated forstoring backup data of volumes having the backup property.

In another example, the determination is made based upon a determinationthat the data is associated with a storage policy. For example, thestorage policy may comprise a mirroring policy specifying that the datacorresponds to mirrored data that is mirrored from a source to adestination. In another example, the storage policy may comprise abackup policy specifying that the data corresponds to backup data thatis backed up from the source to the destination. The second storage tiermay be designated for storing data associated with the mirroring policy,the backup policy, or other type of storage policy.

At 306, the data is stored (e.g., from within memory of a storagesystem, such as a storage controller or node that received a writerequest from a client to write the data into the multi-tier storageenvironment) into a staging area of the first storage tier. The stagingarea may be storage space within the first storage tier that isdesignated for data that is to be stored into the second storage tier.For example, the data is written to a staging file, such as a TLOG file,used to stage blocks that are to be written to the second storage tier.Thus, the data is written into the staging area according to a firststorage tier location identifier (e.g., a first physical volume blocknumber (pvbn), a first file block number, a first virtual volume blocknumber (vvbn), or other storage location format used by the firststorage tier to store and reference data). A file system hosting thedata (e.g., an active file system associated with a volume to which thedata is assigned) is not provided with the first storage tier locationidentifier as a primary reference for identifying the data. Instead, asecond storage tier location identifier (e.g., a second physical volumeblock number (pvbn), a second file block number, a second virtual volumeblock number (vvbn), or other storage location format used by the secondstorage tier such as the remote object store to store and referencedata) is assigned to the data within the staging area, at 308. Thesecond storage tier location identifier is provided to the file system(e.g., the active file system currently providing clients with access todata of the volume) for referencing the data even though the data is notyet stored to the second storage tier.

In an example, a mapping between the first storage tier locationidentifier and the second storage tier location identifier may becreated. The mapping may be utilized to identify the data within thestaging area, such as by the file system. For example, a request may bereceived to access the data before the data is destaged from the stagingarea to the second storage tier. The data may be provided from thestaging area using the mapping to satisfy the request. For example, thefile system may utilize the second storage tier location identifier as alookup into the mapping to identify the first storage tier locationidentifier that can be used to access the data within the staging area.

At 310, the data is destaged from the staging area to the second storagetier. In an example where the second storage tier is a remote objectstore, an object is created within the second storage tier to comprisethe data. A name is created for the object based upon a volumeidentifier of the volume to which the data of the object belongs. Thename may also be based upon a sequence number assigned to the object.Sequence numbers may be monotonically assigned to objects of the volumefor uniquely identifying objects assigned to that particular volume. Forexample, the name may correspond to a hash of the volume identifier andthe sequence number. The object is then stored into the remote objectstore. Because the file system has already been configured to referencethe data using the second storage tier location identifier used by thesecond storage tier to store and reference the data, no additionalchanges need to be made to the file system after the data has beendestaged and stored to the second storage tier. Thus, the file systemcan reference and access the data within the second storage tier usingthe second storage tier location identifier. In an example, the data canbe removed from the staging area based upon a confirmation that the datais stored within the object of the second storage tier.

In one example, a determination is made that the data has adeduplication property indicating that the data has been deduplicated.Accordingly, the deduplication property of the data is maintained whilethe data is stored within the staging area and/or while the data isstored within an object of the second storage tier. In this way,deduplication may be preserved when data is stored into objects of thesecond storage tier.

In another example, a determination is made that the data has acompression property indicating that the data has been compressed.Accordingly, the compression property of the data is maintained whilethe data is stored within the staging area and/or while the data isstored within an object of the second storage tier. In this way,compression may be preserved when data is stored into objects of thesecond storage tier.

In an example, the storage environment, configured to store client datawithin the multi-tier storage environment, may comprise one or moreclusters of nodes that host and/or manage storage devices of the firststorage tier but not the second storage tier. For example, a node mayprovide clients with primary access to data, while a partner node may beconfigured to provide failover operation in place of the node in theevent the node fails (e.g., data may be replicated from the node to thepartner node). An occurrence of a network connection outage may bedetermined (e.g., a loss of connectivity between the node and thepartner node, loss of connectivity from the nodes to the second storagetier, etc.). Accordingly, data received during the network connectionoutage may be stored into the staging area (e.g., the node may storedata into a first staging area accessible to the node during the networkconnection outage, the partner node may store data into a second stagingarea accessible to the partner node during the network connectionoutage, etc.). Monotonically increasing sequence numbers may be assignedto objects that are to store the data within the second storage tier. Inthis way, the objects may be uniquely identified when stored within thesecond storage tier notwithstanding the network connection outage.

A determination may be made that connectivity has been restored.Accordingly, objects may be created with object names derived from thesequence numbers for uniquely identify the objects. The objects may bestored, from the staging area (e.g., from the first and second stagingareas) to the second storage tier, within the objects.

FIGS. 4A-4C illustrate an example of a system 400 for multi-tier writeallocation. FIG. 4A illustrates a storage system 404 that may hostand/or manage a first storage tier 412 (e.g., storage locally accessibleto one or more nodes of one or more clusters associated with the storagesystem 404). The storage system 404 may store data within the firststorage tier 412, such as storing client data into first tier storage416. The storage system 404 may also store data within objects of asecond storage tier 418 such as a remote object store 420 (e.g., storageprovided by a third party storage provider). The first storage tier 412,the second storage tier 418, and/or other storage tiers may be part of amulti-tier storage environment used by the storage system 404 to storedata. The storage system 404 may maintain a metafile 406 comprisinginformation related to the objects, such as sequence numbers assigned toobjects of a volume. The storage system 404 may maintain a volume 410that is exposed to clients. A file system 408 may be associated with thevolume 410.

The storage system 404 may identify data 402 that is to be stored intothe multi-tier storage environment. The storage system 404 may determinethat the data 402 should be stored to the second storage tier 418. In anexample, the storage system 404 may receive an indication from anapplication that the data 402 has a property indicating that the data402 should be stored into the second storage tier 418 (e.g., aninfrequent access property indicative of cold data that should be storedinto the second storage tier 418 that may have higher latency than thefirst storage tier 412 that is better suited for storing frequentlyaccessed hot data). Other indicators may be used to determine that thedata 402 should be stored into the second storage tier 418, such as thedata 402 being associated with a backup volume or mirror destinationvolume, the data 402 being associated with a backup policy or amirroring policy, etc.

Accordingly, the storage system 404 may store 424 the data 402 into astaging area 414 of the first storage tier 412 based upon thedetermination that the data 402 should be stored within the secondstorage tier 418, as illustrated in FIG. 4B. A second tier locationidentifier 422 may be assigned to the data 402. For example, the secondtier location identifier 422 may be provided to the file system 408 forreferencing the data 402 when the data 402 is stored to the secondstorage tier 418. The second tier location identifier 422 may correspondto a format used by the second storage tier 418 for referencing thelocation of data, such as data blocks, stored by the second storage tier418.

FIG. 4C illustrates the storage system 404 destaging 430 the data 402from the staging area 414 into the second storage tier 418. The data 402may be stored into an object 432 that is stored within the remote objectstore 420 of the second storage tier 418. Because the file system 408 isalready configured to reference the data 402 using the second tierlocation identifier 422, the file system 408 does not need to be updatedto maintain consistency. In an example, the data 402 is deleted from thestaging area 414.

Still another embodiment involves a computer-readable medium comprisingprocessor-executable instructions configured to implement one or more ofthe techniques presented herein. An example embodiment of acomputer-readable medium or a computer-readable device that is devisedin these ways is illustrated in FIG. 5 , wherein the implementation 500comprises a computer-readable medium 508, such as a compactdisc-recordable (CD-R), a digital versatile disc-recordable (DVD-R),flash drive, a platter of a hard disk drive, etc., on which is encodedcomputer-readable data 506. This computer-readable data 506, such asbinary data comprising at least one of a zero or a one, in turncomprises a processor-executable computer instructions 504 configured tooperate according to one or more of the principles set forth herein. Insome embodiments, the processor-executable computer instructions 504 areconfigured to perform a method 502, such as at least some of theexemplary method 300 of FIG. 3 , for example. In some embodiments, theprocessor-executable computer instructions 504 are configured toimplement a system, such as at least some of the exemplary system 400 ofFIGS. 4A-4C, for example. Many such computer-readable media arecontemplated to operate in accordance with the techniques presentedherein.

It will be appreciated that processes, architectures and/or proceduresdescribed herein can be implemented in hardware, firmware and/orsoftware. It will also be appreciated that the provisions set forthherein may apply to any type of special-purpose computer (e.g., filehost, storage server and/or storage serving appliance) and/orgeneral-purpose computer, including a standalone computer or portionthereof, embodied as or including a storage system. Moreover, theteachings herein can be configured to a variety of storage systemarchitectures including, but not limited to, a network-attached storageenvironment and/or a storage area network and disk assembly directlyattached to a client or host computer. Storage system should thereforebe taken broadly to include such arrangements in addition to anysubsystems configured to perform a storage function and associated withother equipment or systems.

In some embodiments, methods described and/or illustrated in thisdisclosure may be realized in whole or in part on computer-readablemedia. Computer readable media can include processor-executableinstructions configured to implement one or more of the methodspresented herein, and may include any mechanism for storing this datathat can be thereafter read by a computer system. Examples of computerreadable media include (hard) drives (e.g., accessible via networkattached storage (NAS)), Storage Area Networks (SAN), volatile andnon-volatile memory, such as read-only memory (ROM), random-accessmemory (RAM), electrically erasable programmable read-only memory(EEPROM) and/or flash memory, compact disk read only memory (CD-ROM)s,CD-Rs, compact disk re-writeable (CD-RW)s, DVDs, cassettes, magnetictape, magnetic disk storage, optical or non-optical data storage devicesand/or any other medium which can be used to store data.

Although the subject matter has been described in language specific tostructural features or methodological acts, it is to be understood thatthe subject matter defined in the appended claims is not necessarilylimited to the specific features or acts described above. Rather, thespecific features and acts described above are disclosed as exampleforms of implementing at least some of the claims.

Various operations of embodiments are provided herein. The order inwhich some or all of the operations are described should not beconstrued to imply that these operations are necessarily orderdependent. Alternative ordering will be appreciated given the benefit ofthis description. Further, it will be understood that not all operationsare necessarily present in each embodiment provided herein. Also, itwill be understood that not all operations are necessary in someembodiments.

Furthermore, the claimed subject matter is implemented as a method,apparatus, or article of manufacture using standard application orengineering techniques to produce software, firmware, hardware, or anycombination thereof to control a computer to implement the disclosedsubject matter. The term “article of manufacture” as used herein isintended to encompass a computer application accessible from anycomputer-readable device, carrier, or media. Of course, manymodifications may be made to this configuration without departing fromthe scope or spirit of the claimed subject matter.

As used in this application, the terms “component”, “module,” “system”,“interface”, and the like are generally intended to refer to acomputer-related entity, either hardware, a combination of hardware andsoftware, software, or software in execution. For example, a componentincludes a process running on a processor, a processor, an object, anexecutable, a thread of execution, an application, or a computer. By wayof illustration, both an application running on a controller and thecontroller can be a component. One or more components residing within aprocess or thread of execution and a component may be localized on onecomputer or distributed between two or more computers.

Moreover, “exemplary” is used herein to mean serving as an example,instance, illustration, etc., and not necessarily as advantageous. Asused in this application, “or” is intended to mean an inclusive “or”rather than an exclusive “or”. In addition, “a” and “an” as used in thisapplication are generally be construed to mean “one or more” unlessspecified otherwise or clear from context to be directed to a singularform. Also, at least one of A and B and/or the like generally means A orB and/or both A and B. Furthermore, to the extent that “includes”,“having”, “has”, “with”, or variants thereof are used, such terms areintended to be inclusive in a manner similar to the term “comprising”.

Many modifications may be made to the instant disclosure withoutdeparting from the scope or spirit of the claimed subject matter. Unlessspecified otherwise, “first,” “second,” or the like are not intended toimply a temporal aspect, a spatial aspect, an ordering, etc. Rather,such terms are merely used as identifiers, names, etc. for features,elements, items, etc. For example, a first set of information and asecond set of information generally correspond to set of information Aand set of information B or two different or two identical sets ofinformation or the same set of information.

Also, although the disclosure has been shown and described with respectto one or more implementations, equivalent alterations and modificationswill occur to others skilled in the art based upon a reading andunderstanding of this specification and the annexed drawings. Thedisclosure includes all such modifications and alterations and islimited only by the scope of the following claims. In particular regardto the various functions performed by the above described components(e.g., elements, resources, etc.), the terms used to describe suchcomponents are intended to correspond, unless otherwise indicated, toany component which performs the specified function of the describedcomponent (e.g., that is functionally equivalent), even though notstructurally equivalent to the disclosed structure. In addition, while aparticular feature of the disclosure may have been disclosed withrespect to only one of several implementations, such feature may becombined with one or more other features of the other implementations asmay be desired and advantageous for any given or particular application.

What is claimed is:
 1. A method comprising: in response to determining that data of a first storage location is to be migrated to a second storage location, storing the data as data chunks within object pages of an object; populating the object with a header that comprises at least one of a version of the object, an indicator as to whether the object is encrypted, a creation timestamp for the object, a volume identifier of where the data was stored at the first storage location, and an identifier of a name of the object; storing the object within the second storage location; and reading the identifier within the header in order to determine that the object was successfully stored within the second storage location with non-corrupt data.
 2. The method of claim 1, comprising: populating the object with a context that comprises an encryption key index; utilizing the encryption key index of the context to identify an encryption key; and decrypting the data chunks within the object using the encryption key.
 3. The method of claim 1, comprising: populating the object with a context that comprises a pseudobad indicator; evaluating the pseudobad indicator to determine whether the data read from the first storage location had an error; and in response to determining that the data had the error, designating a data chunk of the object as being inconsistent.
 4. The method of claim 3, comprising: populating the context within an indicator to indicate that a storage operating system marked the error that resulted in the pseudobad indicator.
 5. The method of claim 1, comprising: populating the object with a context comprising an indicator to indicate that a RAID subsystem identified a disk error when reading the data from the first storage location for creating the object; and designating a data chunk of the object as being inconsistent based upon the disk error.
 6. The method of claim 1, comprising: evaluating a context of the object to determine whether the context comprises an unverified error indicator; and in response to the context comprising the unverified error indicator, determining that a data chunk within the object is inconsistent due to an unverified RAID error occurring when the data was read from the first storage location for creating the object.
 7. The method of claim 1, comprising: forcefully corrupting the data stored within the object; and in response to the data being corrupted, setting a wrecked indicator.
 8. The method of claim 1, comprising: identifying a file block number for a data chunk; and populating the object with a context that comprises the file block number.
 9. The method of claim 1, comprising: generating a checksum for a data chunk within the object; and populating the object with a context that comprises the checksum.
 10. The method of claim 1, comprising: creating a context for the object; generating a checksum for the context and a data chunk within the object; and populating the context with the checksum.
 11. A computing device comprising: a memory comprising machine executable code; and a processor coupled to the memory, the processor configured to execute the machine executable code to perform operations comprising: in response to determining that data of a first storage location is to be migrated to a second storage location, storing the data as data chunks within object pages of an object; populating the object with a header that comprises at least one of a version of the object, an indicator as to whether the object is encrypted, a creation timestamp for the object, a volume identifier of where the data was stored at the first storage location, and an identifier of a name of the object; storing the object within the second storage location; and reading the identifier within the header in order to determine that the object was successfully stored within the second storage location with non-corrupt data.
 12. The computing device of claim 11, wherein the operations comprise: evaluating a property of a volume storing the data at the first storage location to determine that the data is backup data to be migrated; and utilizing a destination backup volume at the second storage location as a destination for storing the object based upon the destination backup volume having a backup property.
 13. The computing device of claim 11, wherein the operations comprise: reading the data from the first storage location into a staging file; and destaging the data from the staging file into the object pages of the object as the data chunks. volume having a backup property.
 14. The computing device of claim 11, wherein the operations comprise: in response to determining that the data is deduplicated, preserving deduplication of the data when the data is stored into the object pages of the object as the data chunks.
 15. The computing device of claim 11, wherein the operations comprise: in response to determining that the data is compressed, preserving compression of the data when the data is stored into the object pages of the object as the data chunks.
 16. The computing device of claim 11, wherein the operations comprise: assigning sequence numbers to objects stored within the second storage location, wherein a sequence number assigned to the object uniquely identifies the object.
 17. A non-transitory machine readable medium comprising instructions for performing a method, which when executed by a machine, causes the machine to perform operations comprising: in response to determining that data of a first storage location is to be migrated to a second storage location, storing the data as data chunks within object pages of an object; populating the object with a header that comprises at least one of a version of the object, an indicator as to whether the object is encrypted, a creation timestamp for the object, a volume identifier of where the data was stored at the first storage location, and an identifier of a name of the object; storing the object within the second storage location; and reading the identifier within the header in order to determine that the object was successfully stored within the second storage location with non-corrupt data.
 18. The non-transitory machine readable medium of claim 17, wherein the operations comprise: populating the object with a context that comprises an encryption key index; utilizing the encryption key index of the context to identify an encryption key; and decrypting the data chunks within the object using the encryption key.
 19. The non-transitory machine readable medium of claim 17, wherein the operations comprise: populating the object with a context that comprises a pseudobad indicator; evaluating the pseudobad indicator to determine whether the data read from the first storage location had an error; and in response to determining that the data had the error, designating a data chunk of the object as being inconsistent.
 20. The non-transitory machine readable medium of claim 19, wherein the operations comprise: populating the context within an indicator to indicate that a storage operating system marked the error that resulted in the pseduobad indicator. 